* Bosch claims Mando violates 4 patents in Michigan suit
* Mando issues denial, to "actively respond" to lawsuit
* Mando denial comes after shares skid 13 pct in Seoul (Add Mando denial)
By Hyunjoo Jin
SEOUL, Sept 30 (Reuters) - German auto parts supplier Robert Bosch GmbH lodged a lawsuit in the United States against South Korean peer Mando Corp alleging infringement of four patents, a claim Mando later said was groundless, pledging to "actively respond".
Shares in Mando tumbled 13 percent on Friday to their lowest levels in more than two months after the suit was filed at United States District Court for the Eastern District of Michigan on Thursday.
The suit claims some brake systems (ABS) and electronic stability control (ESC) products supplied by Mando, South Korea's No.2 auto parts maker after Hyundai Mobis, breach four of Bosch's patents.
Bosch said it's seeking an disclosed amount of damages and a court order to prohibit Mando from further infringing the patents. "Unless Mando is enjoined from its infringement, Bosch will continue to suffer irreparable harm," the German firm said in Thursday's filing.
Mando denied the claims in a statement issued in Seoul on Friday, saying it would make an unspecified but "active" response to the lawsuit to resolve the dispute as quickly as possible.
"We will prove that Bosch's claims are groundless should the lawsuit proceed," Mando said in its statement, adding the dispute would not affect the stability of supply of its products to customers.
Mando has two U.S. factories, in Alabama and Georgia, catering to demand from Hyundai Motor and General Motors.
Mando also supplies steering racks for Tesla Motor's Model S vehicles, and is in talks with the U.S. automaker to supply unidentified components to the upcoming Model 3 car, Reuters reported in May. (Reporting by Hyunjoo Jin; Additional reporting by Yun Hwan Chae; Editing by Kenneth Maxwell)